1. What is Magnetic Variation?

Magnetic variation (or declination) is the angle between magnetic north and true north. It varies by location and changes over time due to movements in Earth's magnetic field. This is crucial for aviation navigation as it affects compass readings.

2. How Does the Calculator Work?

The calculator uses the World Magnetic Model (WMM):

Where:

• Latitude — Position north/south of equator (-90° to 90°)
• Longitude — Position east/west of prime meridian (-180° to 180°)
• Altitude — Height above sea level in meters
• Date — Year for which to calculate variation

Explanation: The WMM is a joint product of NOAA and the British Geological Survey that models Earth's magnetic field and its changes over time.

3. Importance for Aviation

Details: Accurate magnetic variation is essential for converting between magnetic and true headings in flight planning and navigation. Errors can lead to significant course deviations.

4. Using the Calculator

Tips: Enter coordinates in decimal degrees (positive for north/east, negative for south/west). Altitude affects the calculation slightly. The model is updated every 5 years (current epoch: 2020-2025).

5. Frequently Asked Questions (FAQ)

Q1: How often does magnetic variation change?
A: Variation changes gradually (secular variation) and the WMM is updated every 5 years to account for these changes.

Q2: What's the typical range of variation values?
A: Variation ranges from about -20° to +20° in most populated areas, but can be greater near the magnetic poles.

Q3: Why does altitude matter?
A: Earth's magnetic field strength decreases with altitude, though the effect on variation is relatively small.

Q4: How accurate is this calculator?
A: Using the official WMM, accuracy is typically 30 minutes of arc, but local anomalies may cause greater errors.

Q5: When should pilots check magnetic variation?
A: Before every flight when planning navigation, especially for long flights or when flying in areas with large variation.